<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
    <style type="text/css">
      .box {
        background-color: red;
      }
    </style>
  </head>
  <body>
    <div id="parent" class="box">parent</div>
    <div id="child" a="1" b="2">
      <div class="box">Child</div>
    </div>
  </body>
</html>
